The present invention relates to an alcohol detection system to detect the level of alcohol consumed by a person. As one example, a drunk driving detection system is provided for a motor vehicle that detects mainly an alcohol drinking condition of the driver.
In recent years, a drunk driving detection system for detecting an alcohol drinking condition of a driver has been developed to reduce the number of accidents caused by drunk driving. Further, studies are made on various systems for controlling the start and operation of a motor vehicle (hereinafter referred to as “vehicle”) based on the output from the drunk driving detection system.
In such a drunk driving detection system, an alcohol sensor detects a concentration of alcohol typically in exhalation. This system utilizes the proportionality between the alcohol concentration in the blood increased by alcohol-drinking and the alcohol concentration in the exhalation. Such types of systems are also used in crackdown of drunk driving. However, in detection of an alcohol drinking condition of a driver by this method, illicit acts cannot be eliminated. Such illicit acts include packing into a balloon the air exhaled by another non-drunk person, or the air exhaled when the driver drinks no alcohol, and blowing the air into the drunk driving detection system. Further, when a drunk driving detection system is installed inside of a vehicle, alcohol contained in the air exhaled by a fellow passenger or in an aromatic substance such as fragrance can cause the system to erroneously detect that the driver is drunk.
A drunk driving detection system is provided that detects an alcohol concentration in the perspiration, which is proportional to the alcohol concentration in the blood, like an alcohol concentration in the exhalation. FIG. 15 is a schematic diagram showing the structure of such a drunk driving detection system.
Sensor elements 105 for detecting alcohol are provided in parts of a steering wheel 101 and a speed change gear knob 103 which are located near the drivers seat of a vehicle and which are to be in contact with the palms of the driver. Each sensor element 105 is made of a pair of electrodes, and an alcohol-sensitive film covering the electrodes. Sensor element 105 utilizes a phenomenon that absorption of an alcohol component to the alcohol-sensitive film changes the resistance between the electrodes. Thus, when the perspiration vapor generated from the palms reaches sensor element 105, the sensor element can detect an alcohol concentration in the perspiration. The output signal from sensor element 105 is transmitted to alcohol concentration measurement unit 107, where an alcohol concentration is obtained. The alcohol concentration output obtained in alcohol concentration measurement unit 107 is transmitted to drunk driving determiner 109, where an alcohol drinking condition of the driver is determined. The determination result is transmitted to post-stage processor 111. If the driver is in a drunk condition, post-stage processing, such as inhibition, warning, prevention, and control of drunk driving, is performed. Specifically, post-stage processor 111 locks the vehicle to inhibit the start thereof, or reduces the speed while the vehicle is running.
In this manner, installation of sensor elements 105 in a steering wheel and a speed change gear knob 103 to be operated by a driver allows the detection of the alcohol concentration in the perspiration of the driver. Thus, the possibility of illicit acts or erroneous detection can be reduced in comparison with the alcohol detection using the exhalation.
Further, after piezoelectric elements or the like disposed in proximity to sensor elements 105 determine whether or not the hand of a driver has touched steering wheel 101, the drunk driving detection system is activated. Thus, the detection accuracy is improved.
Such a drunk driving detection system can detect an alcohol drinking condition of the driver with high accuracy. However, disposition of the piezoelectric elements or the like in proximity to sensor elements 105 causes the following problems. For example, when the driver places the palm on steering wheel 101 so that the palm touches the piezoelectric element but does not touch sensor element 105, the alcohol concentration in the perspiration from the palm is not detected although the drunk driving detection system is activated. As a result, illicit acts for evading detection of an alcohol drinking condition can be performed.